Air or gas blast electric circuit breakers



Sept. 1, 1959 A. RoxBuRGH ET AL 2,902,570

AIR 0R GAS BLAST ELECTRIC CIRCUIT BREAKERS Filed June 23, 1958 5 Sheets-Sheet 1 TTOF/VEV Sept. 1, 1959 A. RoxBuRGl-l ET AL 2,902,570

l AIR oR GAS BLAST ELECTRIC CIRCUIT BREAKERS Filed June 23, 1958 3 Sheets-Sheet 2 '9 20 36 /A/l/f/vro/TS /5 A455177- Poxu H W Sept. l, 1959 A. ROXBURGH ET AL 2,902,570

AIR OR GAS BLAST ELECTRIC CIRCUIT BREAKERS Filed June 2s, 195s s sheets-sheet s HL BERT E H SQICS s .0R AGAS'` BLAST. ELECTRIC i BREAKERS vAlberslmmngh,Willesden Green, Londn, and Athen ALeigh,"l Kenton,l lHarrow;"England, ja'ssrgnors'to The British Thomson-'Houston Company, Limited, London, 'fi 'England, a British company .Application.June.231958, Serial No. .743,759

Glaims priority,n application Great-Britain July "1,'1957 3 Claims. (Cl. 2410-1148) ...This invention relates to.electric..circuit breakers of ,the

v airor gas lblast type. vIt willbe .understood that airis a. i; gasand that rtheoperationzof thecircuit.breaker` described hereafter does not depend upon therchemic'al nature ofthe .V .f gas. :..Thusthe expressions air land .gas mustbe .considered as-.equivalent throughout Afthe. specification, and where cone isefused it.includes the other. asY driving andfarc extinguishing medium, it beingunderstoodthat'in individual 'cases-av gas .ofhigher insulatingquality, such'as nitrogen, mayzbe preferred to air.

.According to the present. invention, an air'or -gas blast electric circuit breaker which comprises a moving main contact adapted to be-separated from.- a co-operating ...main contact -by theapplication .of air .or gas .pressure ...acting on said. Contact or. a piston rmember coupled there- Y. with, has. a .resistance or other impedance,.hereinafter AINconveniently*referred tosimplyas resistance, for con- ,trollingytherecoveryvoltage rise,. or otherwise improving the circuit interrupting characteristics of the inter- ....rnpter, connected.' in .parallel with said main. contacts ,by lmeans ,of-Y an auxiliarycontact karrangement `closing-'the ..circuit through saidsresistancewhen the -mainrcontacts ...are closed,: and V.actuable .directly Arby mechanical means ifromathe..movement:ofsaid.moving;main= contact after the latten-has separated-by ai predetermined; amount :from `.the ,co-joperating1-co-ntact. .The i main; .contacts-.area enlclosedlin a 1.manner-well @known :perfse within Van arc ...chamber gto-Which r-pressure-V aileron-gast is .applied by opening a blast controlxvalve-whenthe circuibisfftoi be nterrupted,-. .and the pressure s air @or 'zgas :then causing @separation ofrfthe. contacts kand ansairori gas blastacross .the contact-gap. p f .,Generally.y thisy invention residesvinn-a :gascblastzgcircuit r11-breaker. `having a movable .main V`contact,.afbiasing ,means .tolforce said. contactaintof engagement-with aufstationary }..main,contact,:and a. contact,.operating mechanism tozrdis- Iaengagesaid :movable contact rfronrithe. stationary-contact, l .saidmechanism being operated-. by .pressure :gas supplied from the same source as the main arc extinguishing .gas blasg whereinaasseries circuit. comprisinggannimpedance #and.auxil1`a 1ry..y contacts Ais connected: acrosszthe main .contacts, 3 and.. a. mechanism controlled by: :the: :movement j of .1..the.gmainac'ontacti is'. provided to-.cause .fopening .rlofzthe I '.auxiliarvcontacts afterf-.dse ngagement ofnthe rmainfcon- .Ltacts and. closing5 rof ...thel .auxiliary contacts z before z rthe mainy contacts close.

- V,.i'rraugements.A according-tonite invention have.; the

, advantage; that..,.the .auxiliary contacts-:areV closedeintrin- .A

as.. a .resulta of..closu1c.\of1 fthefmainccontactsrso ..las,.positive1yto completey the. connectionrofethemesistance ,parallel .with theamain ,contacts;zandwensure'irhatrathe .,cuIrentfpaththrough: .the-resistancer-is; already closed .be-5 5 f lfore: theJnain "contacts beginstowseparate ,fon 1.a;circuit ..opening..operation.

..As `willlhereinatter appear,..=the;invention enables simple l nd...d'cliablemeans -to,-.be,.'.ernployedifor; Vcont-rolling .the

.contacts .in series ,with Ithe resistanceaand .-these-.adyan- ,i

. Patented Sept. .1,`v 1.959

tagesare of considerableimportance. inl-'E.H.T. circuit breakers wherein .there will' commonly bea Iargenumber, for example as many as ten, breaks in eachphase of the circuit breaker.

5 According to a further. featureof the invention, ...the .auxiliary contacts include a moving contact which is adapted to be operatedmechanically 'into engagement with its co-operating contact .bymeans of Va camsurface formed.. on orconnected with4 the moving main contactor 10 a member moving therewith. The moving auxiliary contact is biased, suchv as by a spring, to its openfposition away from the co-operating auxiliary contact. Preferably,

- the carnsurface referredto is arrangedexternallyv of .nan extension of the main moving contact, the latter, for

15.. example,.being. a tubular contact through whichp-the Vair or gas blast is discharged to atmosphere, and the. moving auxiliary..contact or. a camv followermember connected with said auxiliary contact -is arranged to movetrans- .versely, .or to havefa considerable component of its move- 20. .ment transversely, of the movement ,of saidfmainmoving :contact Arrangementsl of this kind possess .thezfurther .advantage'that the main moving contact maybewithdrawn from .the circuitbreaker, such as from thecontact chamber. hereinbefore referred to, without'thediscon- 25. nection or dismantling ofany. internal parts of the circuit breaker, andtfurthermore that after the mainmoving. contact has-been removed it maybe replacedwithout `interference from the operatingmechanismL for-the .auxiliary contacts and will automatically re-engagesuCh operating mechanism for correct operation of the auxiliary contacts.

Conveniently in carrying fout the arrangementVv just .above indicated :the moving. auxiliary contact is connected l.with a-cam follower lever-arranged .to press against the movab1e-auxi1iary contact :through a spring and-to be actuated by a'guidiug surface which movesvin accordance withmovemento-fthe main contact. This guiding surface may convenientlybethe cam: surface of-'thevmainffcon- .fz-tact, although.:in-some.cases,=aswillv be understood, Lthe cam*-surface-may:operateLdirectlyon' the auxiliary mov- .wing contacterwithoutithe interpo'sition fof such lever.

.:In.-a@preferredarrangementfthe main contact -torthe operating mechanism comprises two driving--members'to i; producefrespectively an initial disengagement of thermain 45;- contactsgandtafter a :short interval affurther' increase :of the, distanceibetween thermain contacts,-a'udA the auxiliary `.fcontactzmor'ement is derived" lfrom' a 'motion' producedby the second driving member.

r- LIherinvention-hasgeneralapplication-in air or gas 'blast ozcircuitbreakersabutisferninently -applicable in circuit c rbreakersof the typelwherein afterV the main contacts-` have ,rbeenropened by the airpressure in a contactfchamberthe .eXitzofLthetpressureair from said chamber-is closed so as -arcmnaintain:pressurey 'saidchamberewithout consump- 55 tion of air and thereby hold tllefcontacts'open'under pressure;.:whereby `the circuit in which 'the circuit breaker is: :included imay #be L disconnected continuously without e:opening of series isolators-asvare'otherwiserequired.

in zonee'application-of the-present inventionctol'icircuit mzlrreakers.` arranged as just indicated; Ethemoving cont-actis e arranged :in .accordancefwithr co-pending application No.

317.5133758, thati isi to.; say;Y thermoying-contact 'is provided `l: with a piston area'forme'dby apart-of the-n1o`ving Contact or a member connecteditherewith;said-piston'area'work- Br-.ing .withiniarspacezto which pressureairl is-applied l with a timel'delayiafter application olflpressurer air -to a-pistorr or fequivalentI memberzprovided `for operating the AmainA con- 1 .ztact:in:accordance:with co-pendingi application' -for Letters f.'l?atentrNo.-i692;459. The auxiliary `contactsprovided-ac- ,ewithimam extension oithefwdrking: space for lthepiston area first above referred to and include a contact movable into and out of engagement with a cooperating contact in a direction substantially radially of the movement of the main moving contact, and operable .directly or by a suitable linkage by means of a cam surface formed by an enlargement 'of the main moving contact forming said piston hereby directed.

Figs. 2 and 3 are sectional elevations similar to Fig. 1 but showing the circuit breaker respectively at intermediate and nal stages in the contact opening ope-ration; and

Fig. 4 is a fragmentary sectional elevation corresponding with part of Fig. l and illustrating a modication thereof.

The circuit breaker shown in the drawings comprises a fixed rod-like Contact 1 and a coi-operating movable contact 2 of tubular form arranged within a tubular insulating housing 3. At its right hand end in the iigures the housing 3 is secured to a metal supporting structure 4 in which the contact 1 is fixed. The structure 4 includes internal passages 5 whereby an entry port 6 in said strueture is placed in communication with the interio-r of the housing 3. As Fig. 1 shows, the circuit breaker may be of the otherwise known symmetrical double-break type wherein a second tubular housing partly shown at 3A is also mounted on the structure 4 and encloses a ixed contact 1A with which co-operates a mowing contact (not shown) similar to the contact 2 and having in association therewith similar means as hereinafter to be described for the contact 2. The structure 4 may be mounted at the upper end of a vertical insulating column as is -Well known per se for air blast circuit breakers. This vertical insulating column is of tubular construction providing a through passage in alignment with the entry port 6 and is connected at its foot with an air conduit adapted to be connected by means of a main control valve with an air pressure reservoir. Furthermore, valve means are provided whereby the foot of said insulating column may be placed in direct communication with atmosphere for operation of the circuit breaker in the manner hereinafter to be described.

A control valve is provided for admitting pressure air to the circuit breaker and for discharging the air from the circuit breaker to atmosphere. This valve may be of a known construction, does not form part of the invention, and therefore is not shown.

The tubular moving contact 2 extends through a fixed tubular member 7 having an in-turned end 8 serving to guide the adjacent end of the contact 2. The tubular member r7 is formed with a flange 9 which by means of a clamping ring 10 and suitable studs or the like is rigidly secured to the end of the insulating housing 3 remote from the structure 4.

At its end remote from the iixed contact 1 the moving i secured in place such as by studs and nuts 17` said end cover being provided with a central air discharge port 18 and an external discharge passage 19.`

The moving contact 2 is urged into engagement with f located a sealing gasket 22V adapted as will hereinafter `be described to engage with an annular seating 23 surrounding the port 13. A plurality of ports, such as 24,

are provided within the piston 11 for allowing passage of air during operation as will hereinafter be described. The cylinder 12 includes a portion of reduced diameter providing a further cylinder 25 in which works a piston 26. The piston 26 includes a trunk 27 slidable within the tubular member 7. For a purpose which will hereinafter appear, ports, such as 28, are formed in the ilange 9 for admitting pressure air from the housing 3 to the face of the piston 26. Ports are provided, such as at 29, in the tubular member 7 for admitting such pressure air to the interior of the cylinder 12, it being observed that a substantial annular clearance is provided between the piston trunk 27 and the moving contact 2. The piston Iportion 11 of the moving 4contact includes an annular flange 30 lwhich is adapted to be engaged by the left hand face of the piston 26. Preferably an annular rubber or other resilient cushion 31 is carried by the piston 28 for providing the engagement between said piston and ythe flange 30. A light compression spring is provided at 32 so as totend tomove the piston 26 away from the ilange 30.

For a purpose which will also hereinafter appear a port 12a is provided in the cylinder 12.

The contact 2 may be connected electrically with the assembly 13 by means of a resilient sliding contact assembly or garter spring of any suitable construction indicated diagrammatically at 33.

As so far described the circuit breaker is arranged in accordance with application No. 743,758 aforesaid.

The cylinder 12 |is formed with a lateral extension or antechamber 36 enclosing a lever 37 which is mounted on a xed pin 38. At `itsl free end the lever 37 hasl a pin connection 39 with an actuating member for a movable auxiliary contact'40 which is slidably located for axial movement in a guide member 41 secured to the wall of the antechamber 36. The contact 40 and co-operating fixed auxiliary contact 42 are located within a tubular insulating housing 43 closed at its upper end by a cover plate 44 but in communication with the antechamber 36 by way of ports such as 45 in the member 41. The auxiliary contact 42 is connected with one end of a resistor, shown dagrarnmatically at 46, the other end of which resistor is connected with the assemblyy 4. In the case of a symmetrical double-break circuit breaker such as indicated by Fig. 1 the assembly at the right hand end of the circuit breaker may be arranged similarly to that shown for the left hand end in Fig. 1, a second resistor being partly shown at 46A.

The contact 40 carries an abutment disc 48 between which and the upper end of the member 45 a compression spring 47 acts to tend to move said contact downwardly. The connection between the lever 37 and the contact 40 is effected by -means of a further compression spring 49 acting between the disc 48 and an abutment disc 50 having the pin joint at 39 with said lever. The arrangement comprises an elongated spigot 51 which has telescopic engagement with an `aixal bore in the lower end of the contact 40. f

A roller 52 rotatably carried by the lever 37 engages With vthe piston portion 11 of the main moving contact. The arrangement is such that when the roller 52 is engaged by the peripheral surface of said piston portion as shown in Fig. l the lever 37 will be positioned so as to maintain the contact 40 in engagement with its co-operating contact 42.

Fig. 1 illustrates the circuit breaker ports in the closed condition. In order to open the circuit breaker the control valve referred to is operated to admit pressure air from thereservoir to the housings 3 and 3A. This pressure air ows through the ports 28 so as to move the piston 26 outwardly in its cylinder. The piston 26 is permitted a predetermined distance of free travel before the cushion 31 engages with the ange 30. On engagement of the cushion 31 with the ange 30 the moving contact -member is subjected to an impact due to the 'kinetic-energy possessed by the piston 26 and its truuk V27. vThe'. arrangement .is such that when Y.the moving piston 26.impacts upon the-seating f30` it has..a1ready f fgathered upspeed and-inertia so:that the compression -.;spring-20.is.no longer yable to .maintain the end 2 of. the

moving contact inY engagement with the fixed contact Thus the initial .acceleration of the contact 2 by means .'.of lthe"kineticenergy-imparted to the-piston 26 prior to ".the engagement` of vthe latter with themoving contact member ensures a safey contact vseparation in a manner cmparable'withwhat hasv beenshown in the said `ajtpli- The piston 26and niovingcontact now travel4 together --until .as shown by Fig..2 thepiston-ZG engages withan I.liabutment-formedbyan in-turned ange 34 on the end.

v ofathe cylinder 25. It will .beunderstood that on the -:l previously describedA impact-ofthe piston 26 with the seating30\-a llf-orthe major part vofl the .kinetic .energy t:possessed-at' .that time by ftheypiston will be absorbed. in I `accelerating the moving contact 2. If `desired the cushion 31 may be arranged to engage with' the abutment 34.

Invthe position shown by Fig. l2 the pressure :air` ad- .t-mittedftowthe housing -flows through the. annular` gap between theixed contact lfand the adjacentfend'of` the Y .movingcontact .2 and isdischarged toi atmosphere through* It will be observed that whereas` in the fully closed posi#A tion of Fig. 1 the port `12a isunobstructed by the piston g .11, inthe position shown by Fig. .2 said portuh-asbeen covered'by the piston. N.Consequently the pressure air which is permitted to ilow into said free space will build up pressure in said free space and after a predetermined time period determined by the size of passage in relation to said free volume, said pressure will provide on the piston 11 a force sufficient to overcome the force of the spring 20. When these conditions are reached the piston 11 and moving contact 2 will be moved further in the opening direction so as to bring the sealing gasket 22 into engagement with the seating 23. The gasket 22 and area 21 of the piston then closes the discharge port 18 preventing further discharge of pressure air to atmosphere. The moving contact is retained in the position illustrated in Fig. 3 by the pressure air acting on the area 21 of the piston and the contact will therefore remain open so long as the control valve is opened to apply pressure air to the housing 3.

The operation as so far described is in accordance with application No. 743,758 aforesaid.

When the moving contact reaches the position illustrated by Fig. 2, at which the arc between the main contacts 1 and 2 is extinguished by the air blast, the peripheral surface of the piston portion 11 will have reached a position where the roller 52 is still located for maintaining the auxiliary contact 40 in engagement with the contact 42 but on further movement of the main contact 1 a sloping or conical portion 53 of the piston will move under the roller so that the further movement of the main contact 2 after the pause in the condition shown by Fig. 2, will allow the spring 47 to move the contact 40 downwardly out of engagement with the contact 42. By this means the current owing in the resistor 46 consequent on the opening of the main contact will be interrupted, the auxiliary contacts being fully separated when the main contact reaches the fully open position as shown by Fig. 3. The `separation ofthe auxiliary contacts is effected in a space which as above described is charged with pres- .sure air, namely .by -way of the ports 45', ythe .increase of air pressure .surrounding saidcontacts.:facilitatingthe in- .,terruption .of the resistor current. I

` In order .to reclose the circuit: breaker the controlevlve f isoperated to itsposition discharging-air from ythe housing v3. to..atmosphere. The .pressurefair'within .the housing. 43

.will also be discharged A.toatmospherefsince this air .flows tinto. the'chamber 3. by way-of -theports y35, the clearance flo-f ...the spring.20..and. thereafter the: spring will move the'contact and piston .11 towardathe closed. position. rv-Sosoon the gasket` 22. leaves .therseating 23, air` within the. cir- .cuit `breaker will alsoidischargetoy atmosphere through the ports 24 and.18. Theair pressure-within the housing 43 will .continue to discharge. to. latmosphere .in the-.same way as the air within the tubular housing 3. and additionv.rally when .the .moving contact'reaches the closedxposition `as shown by Fig. l any airremaining-at pressure-within ...saidhousing 43-will be discharged directly-to atmosphere {throughthe vport.12a and `the'port:18wheny said port 12a Iis uncovered bythe pistonll. Ihe circuitbreaker is then .in readiness for subsequent yre-opening. It will Y be `observedrthat .the-.port 71211v provides ythaton reclosure of .thecontacts the` circuittbreaker is .in immediate readiness for.re-openingssince--the uncovering .of the-port 12a enrsuresthat .no-residualpressure -air-will be trapped-and Imaintained inany ofithe-volumes -associated with the Ahousings43as well as housing- 3.

.During-theclosing. movement of y.themain contact 2 .the .cam portion.-53.of..the piston 11 will progressively raise the .lever.-37.so as-to .re-close 4the auxiliary contacts 40,42 when `the main contactA returnsI tothe positionof .Fig..2. v.it will .be observed .that the arrangement ensures lthat the .auxiliary contacts will. be.closed to Are-insert the resistor in circuit in direct Vresponse..to..the :re-closing movement of the main contact 2. It is vthus mechanically impossible for the main contacts to re-close without prior re-closing of the auxiliary contacts.

The connection of the moving contact 40 with the lever 37 by means of the compression spring 49 provides for a predetermined contact force to be obtained in the closed position of the main contact, such spring permitting further movement of the lever 37 by the conical surface 53 after the contact 40 has engaged the fixed contact 42.

In certain circumstances it may be desirable to provide, as is shown by Fig. 4, additional air discharge ports, such as 36, placing the right-hand side of the piston 11 in communication with the interior of the moving contact and said piston. By this means, on movement of the piston 11 from the fully opened position, air at pressure within the housing 43 may discharge directly through such ports 36 and the ports 24, to the port 18 and thereby to atmosphere. The ports 36 thus provide for rapid discharge of air pressure from the housing 43 to atmosphere on reclosing the circuit breaker, and rapid fall of pressure within said chamber 43 so that after an initial movement of the piston 11 away from the seating 23 the spring 20 is relieved of any opposition in reclosing the contacts, or by residual air pressure within the housing 43.

The ports 36 are arranged so as to be covered when the piston 26 engages the flange 30. Consequently during opening operation passage of air through said ports will be terminated when the piston 26 engages said ange and the piston 26 and moving contact move together to the position shown by Fig. 2. In the position of Fig. 2 there is therefore no discharge of air through the ports 36 and the air flows through port 35 to build up pressure in the housing 43 in the manner hereinbefore described.

It is to be noted that with constructions according to the invention such as shown in the accompanying drawings, the moving contact may readily be withdrawn from the circuit breaker. For this purpose it is necessary only to remove the end cover 16 when the spring 20 and contact 2 together with the piston portion 11 thereof ca n be immediately withdrawn from the circuit breaker Without the removal or displacement of any of the other parts associated with the moving contact. Conversely, the movspring 49 and member 50, which member 50 however would then carry a roller corresponding to roller 52 and co-operating with a cam surface on the member 11.

What We claim is:

1. A gas blast circuit breaker having a movable main contact, a biasing means to force said contact into engagement with a stationary main contact, a contact operating mechanism to disengage said movable contact from the stationary contact, said mechanism being operated by pressure gas supplied from the same source as the main arc extinguishing 'gas blast, a series circuit com-| prising an impedance and auxiliary contacts connected across the main contacts, and a mechanism controlled by the movement of the main contact to cause opening of the auxiliary contacts after disengagement of the main contacts and closing of the auxiliary contacts before the main contacts close, wherein the contact operating mecha nism comprises two driving members arranged to become successively effective, the rst member to cause an initial disengagement of the main contacts, and the second member to cause after a short interval an increase in the distance between the main contacts, the mechanism for controlling the auxiliary Contact position being arranged to cause opening of the auxiliary contacts when the second driving member operates to increase the said distance. 2. A circuit breaker as claimed in claim 1 wherein the auxiliary contacts are arranged in a separate chamber which has an inlet port for communication with the arcing chamber of the main contacts and an outlet port for communicating with a passage through which the pressure gas from the main arcing chamber is discharged to the outerv air, the said ports being controlled by the rst and second driving members respectively.

3. A gas blast circuit breaker having a movable main contact, a biasing means to force said contact into engagement with a stationary main contact, a contact op- `erating mechanism to disengage said movable Contact from the stationary contact, said mechanism being operated by pressure gas supplied from the same source as the main arc extinguishing glas blast, a series circuit comprising an impedance and auxiliary contacts connected across the main contacts, and a mechanism controlled by the movement of the main contact to cause opening of the auxiliary contacts after disengagement of the main contacts and closing of the auxiliary contacts before the main contacts close, wherein a means is provided to produce a biasing force which tends to disengage the auxiliary contacts, and the mechanism controlling their position comprises a lever arranged to press through a spring against the movable auxiliary contact and to be actuated by a guiding surface which moves in accordance with the movement of the main contact.

2,447,656 Ludwig et al. Aug. 24, 1948 FOREIGN PATENTS 115,692 Sweden Jan. 22, 1946 

